General properties of some tropical and sub-tropical fruits of Florida

Material Information

General properties of some tropical and sub-tropical fruits of Florida
Series Title:
Bulletin University of Florida. Agricultural Experiment Station
Abbott, O. D ( Ouida Davis ), b. 1892
Place of Publication:
Gainesville Fla
University of Florida Agricultural Experiment Station
Publication Date:
Physical Description:
32 p. : ill. ; 23 cm.


Subjects / Keywords:
Tropical fruit -- Composition ( lcsh )
bibliography ( marcgt )
non-fiction ( marcgt )


Bibliography: p. 31-32.
General Note:
Cover title.
This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
Statement of Responsibility:
by Ouida D. Abbott.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
027182351 ( ALEPH )
18204300 ( OCLC )
AEN4692 ( NOTIS )

Full Text

Bulletin 237

June, 1931

Wilmon Newell, Director





INTRODUCTION ...................................................................................................... 3
COMPOSITION OF FRUITS ...................... ..................................................... 4
A VOCADO ........................................ ........... ................... ....................... 7
CITRUS FRUITS ....................................... ............................................ 12
MANGO ........................ ...................... ...................... ............... 15
PAPAYA .......................... ....................... ......... ... ................. 17
GUAVA ............................................................................... 20
PERSIMMON ....................................................................................... 21
PINEAPPLE ....................................................................... 23
HYGIENE OF FRUIT ........................................ ............ .................. 25
LITERATURE CITED .......................................... ........... ................. 31

Bulletins will be sent free upon application to
the Agricultural Experiment Station


P. K. YONGE, Chairman, Pensacola RAYMER F. MAGUIRE, Orlando
A. H. BLENDING, Bartow FRANK J. WIDEMAN, West Palm Beach
W. B. DAVIS, Perry J. T. DIAMOND, Secretary, Tallahassee

JOHN J. TIGERT, M.A., LL.D., President R. M. FULGHUM, B.S.A., Asst. Editor
H. HAROLD HUME, M.S., Asst. Dir., Re- RUBY NEWHALL, Secretary
search K. H. GRAHAM, Business Manager
S. T. FLEMING, A.B., Asst. Dir., Admin. RACHEL McQUARRIE, Accountant


W. E. STOKES, M.S., Agronomist
W. A. LEUKEL, Ph.D., Associate
G. E. RITCHEY, M.S.A., Assistant*
FRED H. HULL, M.S., Assistant
J. D. WARNER, M.S., Assistant
JOHN P. CAMP, M.S.A., Assistant

A. L. SHEALY, D.V.M., Veterinarian in
E. F. THOMAS, D.V.M., Asst. Veterinarian
R. B. BECKER, Ph.D., Associate in Dairy
W. M. NEAL, Ph.D., Assistant in Animal
C. R. DAWSON, B.S.A., Assistant Dairy
R. W. RUPRECHT, Ph.D., Chemist
R. M. BARNETTE, Ph.D., Associate
C. E. BELL, M.S., Assistant
J. M. COLEMAN, B.S., Assistant
H. W. WINSOR, B.S.A., Assistant
H. W. JONES, B.S., Assistant

E. F. GROSSMAN, M.A., Assistant
P. W. CALHOUN, B.S., Assistant

C. V. NOBLE, Ph.D., Agricultural Economist
BRUCE McKINLEY, A.B., B.S.A., Associate
M. A. BROOKER, Ph.D., Assistant
L. W. GADDUM, Ph.D., Biochemist
C. F. AHMANN, Ph.D., Physiologist
J. R. WATSON, A.M., Entomologist
A. N. TISSOT, M.S., Assistant
H. E. BRATLEY, M.S.A., Assistant
L. W. ZIEGLER, B.S., Assistant
A. F. CAMP, Ph.D., Horticulturist
HAROLD MOWRY, B.S.A., Associate
M. R. ENSIGN, M.S., Assistant
A. L. STAHL, Ph.D., Assistant
G. H. BLACKMON, M.S.A., Pecan Culturist
C. B. VAN CLEEF, M.S.A., Greenhouse
W. B. TISDALE, Ph.D., Plant Pathologist
G. F. WEBER, Ph.D., Associate
A. H. EDDINS, Ph.D., Assistant
K. W. LOUCKS, M.S., Assistant
ERDMAN WEST, M.S., Mycologist

L. O. GRATZ, Ph.D., Asso. Plant Pathologist in charge, Tobacco Exp. Sta. (Quiney)
R. R. KINCAID, M.S., Assistant Plant Pathologist (Quincy)
W. A. CARVER, Ph.D., Assistant Cotton Investigations (Quincy)
RAYMOND M. CROWN, B.S.A., Field Asst., Cotton Investigations (Quincy)
JESSE REEVES, Farm Superintendent, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
GEO. D. RUEHLE, Ph.D., Assistant Plant Pathologist (Lake Alfred)
W. A. KUNTZ, A.M., Assistant Plant Pathologist (Lake Alfred)
B. R. FUDGE, Ph.D., Assistant Chemist (Lake Alfred)
W. L. THOMPSON, B.S.. Assistant Entomologist (Lake Alfred)
R. V. ALLISON, Ph.D., Soils Specialist in charge Everglades Experiment Sta. (Belle Glade)
R. W. KIDDER, B.S., Foreman, Everglades Experiment Station (Belle Glade)
R. N. LOBDELL, M.S., Assistant Entomologist (Belle Glade)
F. D. STEVENS, B.S., Sugarcane Agronomist (Belle Glade)
H. H. WEDGEWORTH, M.S., Associate Plant Pathologist (Belle Glade)
B. A. BOURNE, M.S., Associate Plant Physiologist (Belle Glade)
J. R. NELLER, Ph.D., Associate Biochemist (Belle Glade)
A. DAANE, Ph.D., Associate Agronomist (Belle Glade)
FRED YOUNT, Office Assistant (Belle Glade)
M. R. BEDSOLE, M.S.A., Assistant Chemist (Belle Glade)
A. N. BROOKS, Ph.D., Associate Plant Pathologist (Plant City)
R. E. NOLEN, M.S.A., Field Assistant in Plant Pathology (Plant City)
A. S. RHOADS, Ph.D., Associate Plant Pathologist (Cocoa)
C. M. TUCKER, Ph.D., Associate Plant Pathologist (Hastings)
H. S. WOLFE, Ph.D., Asso. Horticulturist in charge, Sub-Trop. Exp. Sta. (Homestead)
L. R. TOY, B.S.A., Assistant Horticulturist (Homestead)
STACY O. HAWKINS, M.A., Field Assistant in Plant Pathology (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
FRED W. WALKER, Assistant Entomologist (Monticello)
D. A. SANDERS, D.V.M., Associate Veterinarian (West Palm .Beach)
M. N. WALKER, Ph.D., Associate Plant Pathologist (Leeaburg)
W. B. SHIPPY, Ph.D., Assistant Plant Pathologist (Leesburg)
C. C. GOFF, M.S. Assisant Entomologist (Leesburg)
J. W. WILSON, Ph.D., Assistant Entomologist (Pierson)
*In cooperation with U. S. Department of Agriculture.



The realization of the dietetic value of fruits and the increas-
ing demand for greater variety in the diet throughout the year
indicate that fruits peculiar to the tropics and sub-tropics will
be more and more in demand by the peoples of the temperate
zones to supplement their own fruit production. More than 500
edible fruits are found in the tropics and of these less than 50
are in general cultivation, with not more than 20 forming a por-
tion of the food of the masses. There is opportunity, therefore,
for increase in the number of kinds that may be supplied the
markets of colder areas. Improvements in transportation and
refrigeration facilities now make it possible to ship tropical fruits
long distances. Their appearance in northern markets in ever-
increasing amounts must naturally follow. It is indeed fortunate
for the people of the United States that a portion of the country,
the warmer sections of Florida, Texas, and California, are suited
to the production of many tropical and sub-tropical fruits. These
areas by reason of their nearness to large centers of population
are peculiarly fitted to introduce and popularize such fruits as
are or may be grown within their boundaries.
The time when fruits were considered merely as a luxury or
as something to be eaten between meals is passing rapidly and
fruit has now become an indispensable part of the diet. By way
of illustration, it may be pointed out that in 1889 there were
shipped from Florida 2,150,000 boxes of citrus fruits and in 1930-
31 the shipments amounted to more than 27,000,000 boxes. These
figures indicate a decided increase in consumption that cannot
be accounted for on the basis of increased population alone. The
extended use of fruits in the diet is justified by their food value,
palatability, and pleasing appearance. Moreover there are those
who would justify the use of fruit on the score of hygienic or
medicinal virtues. While certain fruits may possess curative
properties, it is not upon that score alone that we need base their
use. It must be admitted that while horticulturists have con-

Florida Agricultural Experiment Station

tribute a vast amount of information on many phases of fruit
growing, the nutritive, medicinal, and hygienic values of fruit
are practically unknown and by many entirely disregarded.
This bulletin is designed to furnish information on the com-
position of certain tropical and sub-tropical fruits grown more
or less extensively in Florida. The data on the composition of
these fruits have been taken as far as possible from analyses
made of fruits grown in Florida; the data on the ash of oranges,
tangerines, and grapefruits are from unpublished analyses made
by Dr. R. W. Ruprecht, Chemist, and the data on the composition
of avocados are from analyses made by Dr. A. L. Stahl, Assist-
ant Horticulturist, Florida Agricultural Experiment Station.
These data have been used in this bulletin with the permission of
these investigators, and the author wishes to express apprecia-
tion for this privilege. Other analytical data have been compiled
from various published sources.
These sources have been carefully and critically viewed. The
figures are as reliable and complete as can be made from the
analyses available. In any attempt to give a representative pic-
ture of groups of fruits the individuals of which may vary wide-
ly, there are, of course, certain limitations. The figures given
represent at best only an estimate of the composition of any par-
ticular fruit. In certain instances, the analyses are incomplete
as some of the constituents were not determined, while in other
cases data representative of a given fruit as a whole are not

Proximate chemical analyses of fruits which include deter-
minations of the percentages of fibre, fat, protein, sugar, water,
and ash furnish a convenient basis for judging their relative food
values. It should be emphasized, however, that fruits contain
many other constituents not determined in such analyses. Among
these are such materials as pectins, glucosides, tannins, enzymes,
vitamins, and traces of rare elements.
From the data presented in Table I it is evident that the water
content of fruits is large in comparison with the total amount of
solids and it will be noted that the percentage of water varies
from 75% in the banana to 89% in the pineapple. The plan of
classifying fruits that contain 80% or more of water as flavor
fruits and those with less than 80% of water as food fruits has
been suggested. At best, such a classification is purely arbi-

Bulletin 237, General Properties of Some Florida Fruits 5

trary as so much depends upon the variety of a given fruit and
the environment under which it has been grown. If in con-
nection with the grouping of fruits into two such classes con-
sideration be given to the general character of the fruit and the
ways in which it is used, then such a classification would be of
value. Based purely upon moisture content, guavas, mangoes,
oranges, strawberries, and pineapples would be classified as flavor
fruits while figs and bananas would be placed as food fruits.
Avocados would be placed with the food fruits in spite of the
fact that under some conditions of soil, climate, and culture the
fruit produced may contain more than 80% moisture. Other
fruits, as the loquat, under certain conditions may contain less
than 80% water. Such occasional variations are not sufficient
reason for transferring a fruit from the group to which it nat-
urally belongs. With this in mind some of the better known trop-
ical and sub-tropical fruits would be classified as follows:
Flavor Fruits: guava, mango, loquat, orange, pineapple.
Food Fruits: avocado, fig, banana, persimmon.

Kind of fruit Water Protein Ether Fiber Ash Total
_______ I_ __ ext. sugars
Avocado .......................... 81 1.0 10.2 .............. .9 1.5
Fig ............................... 79 1.5 .............. .............. .6 15.51
Guava .............................. 82.9 1.3 .7 6.6 .5 6.47
Loquat ............................ 77.9 .2 .............. .6 1.1 11.34
Mango ............................ 87.4 .6 .4 1.2 .5 14.22
Orange ............................ 86 .8 .2 .............. .5 8.70
Pineapple ....................... 89 .4 .3 .4 .3 11.00
Banana ............................ 75 1.3 .6 1.0 .8 12.9
Persimmon .................... 66.1 .8 .7 1.8 .9 31.5

Carbohydrates, of which the most important are starches and
sugars, are the chief food constituents in most fruits. Of sugars
there are several kinds, among which the most important are
cane sugar (sucrose), grape sugar (glucose), and fruit sugar
(levulose). Of these the last two, known to chemists as invert
and reducing sugars, are usually present in equal quantities. The

Florida Agricultural Experiment Station

amount of sugar present in any given fruit will depend upon its
stage of maturity and the soil, climatic, and water conditions
under which it was produced. The starch present in most green
fruits is large, but as the fruits ripen the starch decreases until
it reaches a minimum in the ripe fruit; while this is taking place
the sugars gradually increase.
In certain tissues of such fruits as guavas, citrus, grapes, and
apples another carbohydrate called pectin is found. It is sol-
uble in water. This material causes concentrated water ex-
tracts of fruits to gelatinize or form jelly. The amount of pectin
that may be extracted from a fruit varies with the kind and
variety, the degree of maturity, and the method of extraction.
It is evident that the stage of growth and degree of maturity
have a marked effect on the kinds and amounts of carbohydrates
present in fruits and it is difficult to give average figures repre-
sentative for different types.
There are present in all fruits complex organic substances
capable of exerting catalytic action, to which the name "en-
zymes" has been given. These compounds have a remarkable
property of being able to affect the velocity of a reaction without,
as a rule, undergoing any change themselves. How enzymes are
formed in plants is not known, but all fruits contain them. In
some instances their presence is easily detected, while in others it
is much more difficult. When a pear or apple is cut a dark brown
color appears very shortly afterward on the cut surface. This
is due to a class of enzymes known as "oxidases." Certain en-
zymes are capable of changing starch to sugar, converting fats
into fatty acids and protein into proteoses and peptones. The
specific enzymes found in the fruits discussed in this paper will
be referred to more fully under the discussion of each separate
Another class of compounds found in fruits is called "gluco-
sides." These are more or less complex compounds which, when
hydrolyzed, yield glucose with one or more other materials,
usually of an aromatic nature. The exact function of glucosides
in fruits is unknown. Some of them, or the products of their de-
composition, yield poisonous or bitter products that may serve
as a protection against fruit-eating animals, while antiseptic
decomposition products may have value in preventing the de-
velopment of disease organisms in parts which may be dam-
aged. The glucosides present in the fruits covered by this paper
likewise will be considered with the fruit in which they occur.

Bulletin 237, General Properties of Some Florida Fruits 7

The acids of fruits not determined separately in proximate
analyses vary rather widely, while the avocado and banana con-
tain almost no acid; the guava and mango have an acid content
that varies from .22% to 1.17% while some citrus fruits-
lemons, for instance-may have an acid content as high as 7%.
The total acidity of most fruits is due to the presence of several
acids but each fruit usually has a characteristic, predominant
acid. The principal acid of citrus fruits is citric acid, although
small quantities of tartaric, malic, and other acids are present.
The ash content of fruits, varying from .3% for pineapples
to 1.1 % for loquats, is relatively small. It is made up largely of
potassium, calcium, sodium, magnesium, silica, chlorine, and
iron. That other elements are present, not determined in prox-
imate analyses, is evident from experiments in which the ash
from various fruits has been used in the treatment of certain
types of anemia. This point will be discussed later.
The fat content of most fruits is very small, the outstanding
exceptions being the olive and avocado, which contain large per-
centages. The small amount of material classed as crude fat
(the ether-soluble extract) found in fresh fruits is usually pres-
ent in waxes found on the skin or in the coloring matter.
Most fruits contain one or more vitamins, the exact chemical
nature of which is unknown, as they have not been isolated up
to this time. The specific vitamins present are discussed sep-
arately under each fruit.

AVOCADO (Persea americana)
The avocado is a native of tropical America where it occurs
principally as a seedling door-yard fruit. It belongs to the genus
Persea, family Lauraceae. Other members of the family are cam-
phor, cinnamon, and the native red bay (P. bochinea). Only a
few years ago the avocado was a new fruit on the markets of the
United States, but it is now rapidly taking its place as a standard
salad fruit. It is appetizing, palatable, and nutritious and its ex-
tensive use in the dietary is warranted. To a certain extent it
takes the place of meat in the diets of the people of the West In-
dies and Central America. Because of its high food value and pal-
atability it seems reasonable to predict that eventually it will be-
come as familiar to the housewife as the banana and pineapple.
Up to this time the avocado has been considered a luxury but
when it can be placed upon the market at a popular price and

8 Florida Agricultural Experiment Station

becomes available throughout the year it will come to be re-
garded as a staple rather than a luxury food.

Fig. 1.-The avocado, appetizing, palatable, and nutritious, is coming into
more general use. (Photo by courtesy of the Hort. Dept.)


Kind of fruit

Orange-China ..............

Orange-Florida ..........

Grapefruit ....................

Grapefruit-Florida ....

Guava ............................

Pineapple ......................

Tangerine-Florida ......





















% %
.0533 .027

.0609 .018

.028 .015

.056 .019

.020 .013

.039 .023

.074 .017







. .-.
2 cw










*Ash analysis of Florida fruit by Ruprecht. (Personal communication.) Ash analysis of other fruits calculated from
data by Chace, Tolman and Munson. (1')
IFigures in parentheses (italic) refer to "Literature Cited", page 31.

Florida Agricultural Experiment Station

In presenting the data on the composition of avocados grown
in Florida it should be explained that the proportions of con-
stituents have been found to vary rather widely even in the same
variety, depending upon the location of the trees, kind of soil,
the maturity of fruit, moisture, temperature, and other factors.
The data given in Table III for the varieties grown in Florida
at the places mentioned show that:
1. The moisture varies from 68% to 83%. This means the
total solid matter varies from 17% to 32%, with an approximate
average of 28.5%. The banana is perhaps the only other fruit
that compares in this particular with the avocado.
2. The protein content, varying from 1.2% to 1.6%, is some-
what higher than in other fresh fruits. It is interesting to note,
according to Jones and Gersdorff (8) that the quality of this
protein is high, since it contains the following amino-acids-
cystine, lysine, trytophane, and tyrosine.
3. The amount of mineral matter is higher than in most other
fresh fruits, varying from 1% to 1.8%. According to Jaffa and
Goss (7) more than one-half of the ash of the avocado is com-
posed of sodium, potassium, calcium and magnesium, thus plac-
ing this fruit among those foods yielding an excess of base-form-
ing elements, as contrasted with meat, eggs, and nuts, which fur-
nish an excess of acid-forming elements.
4. The amount of carbohydrates is low as compared with that
of many other fruits. This is due to the absence of starch and
a low total sugar content, 1.4% to 1.9%. A new sugar, believed
to be present in amounts varying from .5% to 1%, to which the
name D. mannoketoheptose was given, has been isolated by La-
Forge, Bureau of Chemistry, United States Department of Ag-
5. The chief value of the avocado as a food lies in its high
fat content, which varies from 7% to 23% on a green basis or
from 37% to 70% on a dry basis. Variation is particularly
noticeable in the fat content. The principal factors influencing
the presence of this constituent are the variety, stage of matur-
ity, and the conditions -under which it has been grown. The fat
content, low in the immature fruit, increases up to maturity, and
after this point is reached there is no further increase no matter
how long it may remain on the tree. Preliminary analyses by
Stahl conducted at this Station indicate that avocado oil has a
high iodine number, which means that there are unsaturated
fats present.

Bulletin 237, General Properties of Some Florida Fruits 11

Weatherby (18) has found vitamin D in avocado oil. It is not
to be implied that the oil is on a par with cod liver oil in the
cure of rickets, but the fact that avocados are a food source for
this vitamin is worthy of consideration. Avocado oil has been
found to be as digestible as other edible oils, 93.8%o, which places
it on a par with butter. Wright and Mitchell (25) state that
avocado oil is very similar to laurel butter and bayberry fat.

R CS 02
Variety of grove ,

b o = = 0 k W 0

Guatemalan Race (Persea americana) Average of 50 fruits.

Eagle Rockl Lake Placid 565 13 13 74 13 55 76 1.8 1.6 1.0 Dec.
Wagner....... Lake Placid 319 23 13 64 23 70 68 1.9 1.2 1.2 Dec.

West Indian Race (P. americana) Average of 25 fruits.

Trapp........... Homestead 460 16 9 75 11 40 82 1.6 1.3 1.0 Nov.
Waldin......... Homestead 497 23 9 68 7 37 83 1.4 1.2 1.1 Sept.
Hybrids Persea spp. Average of 25 Collinson and 35 Lula fruits.

Collinson..... Homestead 594 11 9 80 11 50 79 1.7 1.2 1.3 Oct.
Lula............. Lake Placid 482 22 10 68 17 58 70 1.9 1.6 1.8 Nov.

*Personal communication.

Weatherby, Youtz and Watson (19) report that vitamins A,
B, and E have been found in avocados in small amounts. Ac-
cording to their investigations avocados contain sufficient vit-
amin C to defer severe symptoms of scurvy for a short period,
but not sufficient to be considered as a protective against scurvy
in the quantities that can be consumed.

Florida Agricultural Experiment Station

Citrus fruits are one of the oldest groups of fruits in culti-
vation. So far as known they were first domesticated in south-
ern and southeastern Asia. The orange probably had its origin
in southeastern Asia from which area it was taken to Europe
and thence to America many years ago. Thus far the origin of
the grapefruit remains a mystery, though it is regarded as a
West Indian sport from the Shaddock. The Mandarin group,
to which the King orange, the common mandarin, the tangerine,
and the satsuma belong, was first brought from Canton, China
early in the eighteenth century. There are many other interest-
ing fruits belonging to the citrus family, but only the grape-
fruit, orange, and tangerine will be considered here.
From the data given on the composition of Florida grown cit-
rus fruits in Table IV, it is evident that such factors as variety
and the degree of maturity-the latter depending to some ex-
tent on the location of the trees, soil, moisture, kind and amount
of fertilizer-determine the percentage of juice, acid, sugars,
and other compounds present in these fruits at any time. In
Table I it is shown that oranges, tangerines, and grapefruit all
contain more than 80% of water; hence they are classed as
"flavor fruits". The percentages of ash in citrus fruits (Table
II) are not so high as the percentages of ash in avocados or
guavas. It will be noted that the ash is high in potassium, and
contains calcium, magnesium, and sodium in appreciable amounts.
These elements contribute to the potential alkalinity or surplus
of base-forming elements.
The total sugars in these three fruits is low in comparison
with most fruits but higher than is found in the avocado and
is about the same as for the pineapple and guava.
The percentages of protein and fat are not given in the tables.
Sherman (15) gives the average percentage of protein for the
orange as .8% and for the fat .2%, while Zoller (26) gives the
average percentage of protein in the grapefruit as .3%.
In Table IV data are presented which show that the percentage
of acid is high, while the percentage of sugar is low at the be-
ginning of the season for all citrus fruits considered; as the
fruits mature the reverse is true: acid decreases and sugar in-
creases. The principal acid of citrus fruit is citric acid, but
traces of malic, tartaric, and oxalic acids are present.
From steamed, distilled grapefruit oil the following compounds
have been identified by Zoller (26): Pinene, limoline, linalool,


? ca

Fig. 2.--Florida citrus fruits contain plenty of vitamins and other health-giving properties.

14 Florida Agricultural Experiment Station

citral, geronial, and traces of citronellal, linalyl, and geranyl
esters. The following compounds have been found in the oils
of sweet orange by Willimott and Wolkes (22): Limonene, cit-
ronellal, and methyl anthranilate esters. All of these are com-
plex organic compounds, some of which are found in crude tur-
Dat % -% Ratio
Date % % Reduc- % 1 acid
1912 Juice Taste Acidity Sucrose ing Total to
Sugar Sugar Sugar

Parson Brown
Sept. 28........-. 50.5 tart 0.86 3.05 2.42 5.63 6.5
Nov. 13 .............. 55.8 sweet 0.66 4.76 3.16 8.17 12.4
Dec. 31.............. 56.5 sweet 0.53 4.98 3.48 8.72 16.4
Nov. 13.............. 51.9 tart 1.02 3.86 3.24 7.31 7.1
Dec. 31............. 49.8 sweet 0.77 4.57 3.65 8.46 10.9
Jan. 28, 1912. 47.2 sweet 0.63 5.15 4.13 9.56 15.1
Oct. 16.............. 52.6 v. sour 2.13 1.45 2.62 4.14 1.9
Dec. 19 ............. 59.8 sour 1.46 4.07 3.77 8.05 5.5
Feb. 19, 1913.. 58.5 sweet 1.08 5.39 4.53 10.21 9.4
Apr. 24, 1913.. 59.6 sweet 0.84 5.75 5.13 11.18 13.3
Nov. 21............. 53.3 tart 0.99 3.87 2.30 6.37 6.4
Dec. 19 ......... 57.7 tart 0.81 4.90 2.22 7.38 9.1
Silver Cluster
Oct. 3.............. 45.4 sour 1.13 2.77 2.73 5.65 5.0
Dec. 5............ 48.1 sour 1.17 2.91 3.16 6.22 5.3
Feb. 6, 1913. 53.6 tart 1.04 3.16 3.11 6.44 6.2
May 1, 1913. 53.5 tart 0.94 2.67 3.97 6.78 7.2

In the preparation of pectin from grapefruit there may be
noticed in the flasks containing hot water extract of the inner
white portions of the fruit (albedo) numerous rosettes of small
white crystals. After several re-crystallizations from water and
finally from alcohol microscopic examination shows glistening
white mono-clinic crystals. The name naringin was given to
these glucoside crystals by Hoffman in 1857. Naringin is ex-
ceedingly bitter and even in dilutions of 1 to 10,000 with water
the bitter taste is still present. The glucoside hesperidin has

Bulletin 237, General Properties of Some Florida Fruits 15

been isolated from oranges and lemons. In Table XI data on the
vitamin content of citrus fruits are given. According to Morgan
and Chaney (13) grapefruit or grapefruit juice is an excellent
source of vitamin B. However, the data on vitamin A content of
grapefruit indicate that it is absent or that it is present only
in very small quantities. From the work of Willimott (23 and
24) it is evident that orange juice, either concentrated or fresh,
furnishes an abundance of vitamin C and is a good source of
vitamins A and B. Very little work has been done on the vita-
min content of tangerines. The results of Delf (3) are conclusive,
however, that tangerines are an excellent source of vitamin C.

MANGO (Mangifera indica)

In 1727 Hamilton wrote, "The Goa mango is reckoned the larg-
est and the most delicious to the taste of any in the world and
I may add the wholesomest and best tasting fruit in the world."
The natural habitat of the mango is believed to be northern
tropical India and eastward. One of the earliest pieces of San-
skrit literature records the fact that an Indian Rajah was so
delighted with a certain variety of mango that he recommended
that all the highways be planted with the fruit. That large
plantings of mango trees were made at a time when fruit or-
chards were practically unknown bears testimony to the popu-
larity of the fruit at a very early date. The mango belongs to
the family Anacardiaceae or Cashew family and has probably
been in cultivation for five or six thousand years.
Some of the varieties are bland and fiberless like the Caraboa
of the Philippines, while others are stringy with a strongly
resinous or turpentine flavor. The mango is to the tropics what
the apple is to the temperate zones.
In Table V it is shown that while the percentage of the edible
portion of the mango may vary, fruits from different parts of
the world have a rather definite composition.
The food constituent most abundant in the mango is sugar,
which varies from 11% to 18%. The mango is one of the few
fruits in which sucrose is the principal sugar. One of its pe-
culiar characteristics is the small quantity of starch present.
Some investigators report the entire absence of starch in the
ripe fruit of some varieties. Another carbohydrate found in the
mango is pectin, which is present in the partly ripe fruits in
sufficient amounts to make excellent jellies.

Florida Agricultural Experiment Station

Fig. 3.-The mango is wholesome and delicious. (Photo by courtesy of
Hort. Dept.)
The acid of the mango, calculated as sulphuric acid, lies be-
tween .22% and 1.05%, the principal acid being citric. The
amount present in ripe fruit is too small to make first class jelly,
and lime or lemon juice is usually added to mango juice in jelly
making. The unripe fruit contains malic and tartaric acids in
considerable quantities. The unripe fruit also contains tannin,
which causes the fruit to be slightly astringent at that stage,
but in the fully ripe fruits of most varieties this quality is not
The mango contains an antiscorbutic principle which makes it
a valuable fruit because of its wide distribution in the tropics.
It has been claimed that the mango will cure advanced cases of
scurvy where all'other fruits have failed.

Bulletin 237, General Properties of Some Florida Fruits 17

RIETIES OF MANGOES (Mangifera indica).

Variety 0 0
o o

Grown in Hawaii. Analyses by Thompson (16).

Pairi ....... 60 20.52 0.343 0.22 0.456 14.78 0.032
Alphonse .. 67.48 20.92 0.469 0.373 0.919 14.64 0.149
Totapari .......... 60.19 15.27 0.277 0.578 0.475 11.48 0.065
Grown in Philippine Islands. Analyses by Wester (20).

Caraboa .......... 73 17.20 0.45 ............- 0.22 13.24 .............
Pico ............ 73 23.6 0.40 ............ 0.75 18.40 .........
Pahutan .......... 60 25.70 0.53 1.12 17.54
Grown in Jamaica. Analyses by Chace, Tolman and Munson (1).

No. 11 ............ 59.9 18.73 0.38 0.96 :........... 12.11 .......
Bombay ......... 65.1 18.81 0.35 0.98 ........... 12.7P .... ..
Black .............. 53.6 22.35 0.20 1.058 ............ 16.(

PAPAYA (Carica papaya)

The papaya, known to botanists as Carica papaya, belongs
to the family Caricaceae and is rather closely related to the
Cucurbitaceae or melon family. In Hawaii and other tropical
countries the papaya replaces the northern cantaloupe and the
better varieties are a worthy rival of that fruit. It possesses
an excellent flavor with a pleasing, slightly musky tang. Its
original habitat is more or less uncertain. Dutch travelers in
1598 found papayas in the Spanish Indies and since then they
have spread wherever climate and soil have been found suitable
for their cultivation.
In Table VI it is shown that papayas are flavor fruits contain-
ing 86 to 88% water. They contain little actual nourishment but
because of their high water content and the acids and salts
present they are cooling and refreshing.
One peculiarity of the papaya is the lack of any appreciable
amount of starch in either green or ripe fruit. Whether the
enzymes change the starch into sugar as fast as it is formed in
the fruit or whether the starch is changed into sugar in the
leaves and translocated to the fruit or whether starch is formed

Florida Agricultural Experiment Station

at any time is entirely a matter of speculation. However, it
has been found that when papayas that have reached their full
size, as far as could be judged, were taken from the trees at the
beginning of the ripening process, no increase in sugar content
took place, though the flesh softened, the green color of the fruit
changed to yellow, and it had a pleasingly ripe odor. Because
of this peculiarity and the difficulty in handling the fully ripened
fruit, the satisfactory transportation of papayas to remote
markets must be rapid and accompanied with extreme care in
In Table VI it is shown that ash, protein, and acids occur in
small quantities and that there is very little difference in the
amounts present in immature and in fully ripe fruit. The total
solids increased during the ripening process from 6.48% in the
fruit five months before it is ripe to 10% or 14% in the ripe
S! Sugars
4J.. 0- -- j
*g"g 42 ,5 I 02 .a 1

5 months .. 71 6.48 .621 .065 .800 2.15 .23 2.38 .205 .873
1 month .... 81 6.13 .427 .045 .388 2.81 .23 3.04 .188 .692
8 days ...... 84 8.92 .508 .033 .356 5.99 None 5.99 .163 .654
Ripe .......... 83 10.59 .565 .059 .388 8.02 None 8.02 .186 .693
Strains papaya
Trinidad ........... 12.14 .53 .06 .43 .................. 9.72 .06 .78
South Africa .... 13.00 .54 .09 .68 ....................10.73 .07 .81
Honolulu ........ 12.20 .56 .07 .50 .................... 10.29 .05 .66
Barbados .......... 11.72 .48 .06 .46 .................. 8.95 .06 .76
Panama .............. 14.41 .90 .14 .50 .................... 11.12 .25 1.09

According to Miller (10) papayas contain vitamins A and B
in appreciable amounts and are an excellent source of vitamin C.
Immature fruits, leaves and stems as well as other parts of the
papaya plant yield a white, milky juice, or latex, in which an
unusual protein digesting enzyme called papain is present. Fully
ripe fruit does not yield latex and that obtained from nearly ripe
fruit does not contain the enzyme in an active state. If, how-
ever, juice from the interior of the plant which in itself has
little or no activity is mixed with the latex from nearly ripe fruit,

Bulletin 237, General Properties of Some Florida Fruits 19

the addition of this activator causes the mixture to become ac-
tive so it will digest proteins and act exactly as the latex from
immature fruit in which both enzyme and activator are present.
Just what value the enzyme is to the papaya plant is merely a
matter of conjecture.

Fig. 4.-The guava is an excellent jelly fruit. (From Bul. 223.)
Long ago the natives of tropical countries where papayas are
grown found that rubbing tough meat with a slice of green fruit
made it tender. They also used the latex in the treatment of
various diseases and digestive troubles. The pulp of ripe fruit
applied to the skin is said to remove blemishes and freckles.

Florida Agricultural Experiment Station

Perhaps no other plant family contains so many plants of a
dietetic value as the family Myrtaceae, to which the guava be-
longs. Among its close relatives are the plants yielding cloves,
allspice, nutmeg, and such fruit plants as downy myrtle, suri-
nam cherry, feijoa, and roseapple. The guava was probably cul-
tivated by pre-Inca people and had spread all over tropical
America before the coming of the first explorers. It is now a
common fruit in nearly every tropical country, whether it be
wet or dry, high or low, and in many areas it has become feral
(wild). The guava is pre-eminently a jelly fruit; the great
natural advantage possessed by the fruit lies in its acid-pectin
balance. The acid and pectin are so concentrated that three
times the weight in sugar may be added to the juice and it is
estimated that 100 pounds of fresh acid guavas will yield 350
pounds of jelly. Guavas are often extracted three or four times
and the fourth extraction yields an acceptable jelly.

0 r.

Common guava
guajava)...... 84 17.78 .531 .363 1.125 6.61 .77 7.38 .524 4.445
White .............. 87 18.75 .676 .451 1.525 5.73 2.53 8.26 .412 5.105
Cattleianum) 98 18.27 .742 1.171 1.038 2.41 2.05 4.46 .554 6.146
guava ............ 81 23.75 .755 .715 1.838 2.32 3.31 5.63 .790 9.378

In Table I it is shown that guavas contain approximately
80% of water and hence are flavor fruits. Guavas have a char-
acteristic flavor and odor in the fresh fruit which to some are
objectionable. Depending upon the variety, guavas may be
decidedly sweet or very acid; the common guava contains about
.36% acid and the strawberry guava about 1.17%o acid. In the

Bulletin 237, General Properties of Some Florida Fruits 21

strawberry guava the total sugars are decidedly low, 4.46% to
5.6 %; while the reducing sugar and sucrose are present in about
equal amounts.
The ash of the guava is a little higher than for most fruits
and varies from .53% to .84%. The ash shows nothing char-
acteristic, though it contains more than the average amount of
potassium, which contributes to the potential alkalinity of the
PERSIMMON (Diospyros kaki)
The oriental persimmon is a native of China, Japan, and Korea.
Certain valleys in China are given over to the cultivation of the
persimmon while in Japan it is grown mostly as a door-yard fruit.
It has been cultivated for years in both China and Japan, but it is
from the latter country that we have received most of our in-
formation on this fruit. The persimmon belongs to the family
Ebonaceae or ebony family, and to the genus Diospyros. The
ebony wood of commerce and the native persimmon of America
also belong to this genus.
The average composition of several varieties of persimmons
grown in Florida is given in Table VIII. The percentages of
sugar are very high. This is almost entirely due to glucose, as
repeated tests have failed to show even a trace of cane sugar.
Some varieties of the native American persimmon have a some-
what higher sugar content than is found in the Japanese sorts.
The acid content is low even in the green fruit.
The water content is low when compared with other fruits
contained in this study. The Hachiya contains approximately
71% and Yemon 76%. Hence the persimmon is placed among
the food fruits.
Solids in the persimmon are high, varying from 18.52% in
Tanenashi to 25.06% in Hachiya, while the ash and protein con-
tent are low. One of the constituents of persimmons that is of
particular interest is tannin. The table shows that in the ripe
persimmon the percentage of tannin varies from .41% in Zengi
to 1.54% in Tsuru. The tannin occurs in specialized paren-
chyma cells which differ slightly in size from the ordinary paren-
chyma cells. In the oriental persimmon these cells are commonly
cigar-shaped and in some cases are five to ten times as long as
wide, the actual length often being 1 mm. Tannin is not localized
in the green fruit but is abundant in the cell sap of certain cells
and according to some investigators in the spaces between the
cells. Later the tannin collects in these specialized tannin cells.

Florida Agricultural Experiment Station

In the green fruit the presence of tannin is very noticeable but
in ripe fruit, the tannin content of which has changed little if
any, the astringent effects are not perceptible. A number of
theories have been advanced to explain this but the generally
accepted one is that in the green fruit the tannin is soluble in
the saliva but after the fruit matures the tannin becomes oxi-
dized or changed in some way to an insoluble form.

Fig. 5.-The persimmon contains a high content of sugar. This is a
specimen of the Japanese persimmon. (From Bul. 205.)

Bulletin 237, General Properties of Some Florida Fruits 23



Analyses by McBryde (9)

Hachiya ..-....... 71.77 16.83 0.93 0.88 ------------ ............ 0.1 .........
Tsuru ........... 73.46 15.67 0.74 0.64 ....0.1 .........
Hyakume ...... 70.17 17.83 1.10 1.15 ........... .... 0.1
Yemon ............ 76.26 15.99 0.45 0.60 0.1
Analyses by Gore (4)

Hachiya ....... ...... 17.71* 0.64 0.49 ............ 25.0 .... 0.88
Tane-nashi .... ......... 14.59 0.42 0.39 ............ 18.52 ........ 0.13
Triumph ........ ------------14.74 0.40 0.41 ............20.82 ........ 1.39
Tsuru .... ....... ........ 14.46 0.61 0.46 ............ 21.08 1.54
Zengi .............. 14.72 0.73 0.49 ............ 21.83 ........ .41
Analyses by Tilt and Hubbell (17)

Okami --............ 78.42 16.70** 0.869 0.461 0.213 ............ ........ ..........
Tane-nashi .... 81.43 13.41 0.431 0.335 0.298 ............ ........ ..........
Fuyugaki ...... 81.35 16.04 0.612 0.444 0.111 ............ .--- ..........
Triumph ........ 77.06 15.87 0.658 0.513 0.488 ............ ....... ..........
Zengi .............. 76.27 17.39 0.626 0.523 0.206 .......... ........ ..........
Tsuru .............. 80.23 11.55 0.735 0.576 ............ ............
Tamopan ........ 81.71 13.81 0.669 0.304 0.337 ........... ....... ..........
*Sugar calculated as invert sugar.
**Sugar calculated as dextrose.

Very little work has been done on the vitamin content of per-
simmons, though the results of Iwasaki (6) appear to indicate
the presence of some vitamin C.

PINEAPPLE (Ananas sativus)
It is generally conceded by botanists that the pineapple is a
native American fruit and since all its close relatives are native
to America it would appear strange were it not found in some
of the regions where closely related plants are indigenous. The
pineapple belongs to the family Bromeliaceae and is closely
related to Tillansia, the Spanish moss so common in the southern
states. The name pineapple was first applied to the fruit by
the Spaniards because of its resemblance to a pine cone. In
Table X is shown the composition of pineapples at different

Florida Agricultural Experiment Station

stages of maturity. Of particular interest in these data is the
small percentage of sugar, both invert and sucrose, in the green
fruit, though the amount of sucrose in the ripe fruit is much
greater than in most fruits. In Table IX it is shown that the
total sugars vary to a considerable extent in the same variety.



Red Spanish ......
Red Spanish ......
Porto Rico ..........
Egyptian Queen
Red Spanish ......
Blood .................
Red Spanish ......
Red Spanish ......
Egyptian Queen..
Red Spanish ......

, m









Analyses by Hume and Miller (5)

Abachi ........... 11.98 0.58 0.41 1.05 ............. 10.55
Spanish .......... 12.64 1.20 0.46 1.35 ............. 10.22
Cayenne .............. 14.40 1.02 0.42 0.60 ............. 13.37
Egyptian ............ 16.00 1.99 0.43 0.81 ............. 12.21
Porto Rico ....... 13.60 1.38 0.47 0.76 ............. 11.61
Sugar Loaf ........ 10.76 1.00 0.48 2.11 ................ 8.49



Maturity of 3 "s w
the fruit .. e

Average compo-
sition of the
green fruit ................ 0.39 0.17 6.89 5.80 3.29 1.72 5.01
Gathered green and
allowed to ripen .... 0.58 0.22 6.45 4.35 1.22 3.90 4.12
V4 ripe on plant ...... 0.65 ............ 8.68 ........... 2.74 4.42 7.16
% ripe on plant ........ 0.65 .. ................... 2.97 6.74 9.71
Ripened on plant ........ 0.74 ............ ......... ...... 4.23 7.88 12.11

Bulletin 237, General Properties of Some Florzda Fruits 25

For instance, the sugar content of the red Spanish pineapple
may vary from 8.24% to 15.28%. The difference in the degree
of ripeness and whether the pineapple has been fully ripened on
the plant may account for these variations. The percentages of
hydrolyzable carbohydrates show that the reserve of carbo-
hydrates in the growing pineapple fruit is small and if it be cut
from the plant at this time it cannot develop a high sugar con-
tent in later ripening. From close examination of the pineapple
fruit it has been found that there is no reserve material in it
capable of giving rise to sugar, only faint traces of starch being
found at any time, but that large amounts of starch are present
in the stalks and in the bases of the leaves. The total solids,
the insoluble solids, the ash, and the proteins, are much more
There is some variation in the acid content as shown in Table
IX, the principal acid being citric, though small quantities of tar-
taric and malic acid are also present.
Miller (11 and 12) has found that pineapples either fresh or
canned are a good source of vitamins A, B, and C.
It is shown in Table II that there is nothing characteristic
about the ash of pineapple, though the amount of potassium is
higher than in the average fruit. In the light of more recent
work on the value of apricot and pineapple ash in curing certain
types of anaemia it is evident that the analysis of the ash of
fruits and vegetables must be extended to include many of the
elements heretofore not included. In the pineapple a protein-
splitting enzyme, bromelin, a powerful digestive of albuminous
matter, has been found. The bromelin changes proteins to poly-
peptids, peptones, and amino acids. The amino acids, leucine,
and tyrosine have been identified. Bromelin is active in acid or
alkaline media but is most active in neutral media. It will digest
at 300C. but is destroyed when the temperature rises above 700
C. and is most active between 50 and 600C. The housewife is
familiar with the action of this enzyme. When fresh pineapple
pulp or juice is added to gelatin, cooled below 700, it is noticed
that after 24 hours the gelatin is becoming liquid. This is
brought about by the action of the enzyme bromelin.

The skin and pulp of fruits serve as a protection to the seed
and at the same time by their color and odor when ripe attract
birds, insects, and higher animals to help in their liberation and

Florida Agricultural Experiment Station

distribution. It therefore follows that, due to the selective pro-
cesses of many years, the aesthetic qualities of fruits have be-
come predominant over the strictly nutritive values, though
generally speaking the pulpy fruits are nourishing and palatable
as well as-ornamental. While there is a growing interest in the
food value and hygiene of fruits, they must have more than
aesthetic qualities to recommend them if they are to maintain
a well defined place in the diet.
Most fruits, because of the peculiar blending of acids and acid
salts with sugars and aromatic compounds, are refreshing and
appetizing. It is commonly conceded that most fruits are lax-
ative. The constituents contributing to this property are high
percentage of water, salts in solution, acids, mucilages, gums,
celluloses, and related compounds. In the skins of certain fruits,
some species of plums and apples, there are astringent sub-
stances, tannins and related compounds, which may counteract
the laxative effect of the raw fruit. In such cases the fruit may
be peeled or cooked before being eaten. However, if the peel
of fruit be edible it should be eaten, as the greatest concentration
of salts is to be found in the peel and in the cells immediately
beneath it.
Considerable bulk is an essential factor in the diet. If all the
food eaten were digested and absorbed, elimination from the
intestines would be retarded and serious complications would
result. For this reason bulky foods, such as fresh fruits and
vegetables, are important because they contain a relatively large
amount of cellulose and related compounds which stimulate me-
chanically and render operative peristaltic action. However,
if the fruit be unripe the physiological and mechanical effects
may be very different. Many diverse views are held as to the
exact nature of the ripening processes and of the products
formed. In general, ripe fruits contain less free acid, less starch,
tannin, cellulose, and pectic materials than green fruit and cor-
respondingly greater amounts of sugar. If unripe fruit be taken
into the system the amounts of starch and cellulose are large, di-
gestion may be prolonged and the opportunity for excess fermen-
tation is increased. The excess acid in unripe fruit produces
large amounts of salts irritating to the intestines and may be the
chief factor in causing diarrhea and colic. If the cellulose and
acids be present in more moderate amounts, as in ripe fruits, the
gentle stimulation is beneficial.
Fresh fruits tend to prevent or correct excessive intestinal

Bulletin 237, General Properties of Some Florida Fruits 27

putrefaction. When meat forms a large part of the diet of people
of sedentary habits, excessive intestinal putrefaction sometimes
occurs. Fresh fruit tends to prevent or correct this by increas-
ing peristaltic action and by furnishing a medium less favorable
to the growth of putrefactive bacteria. Excessive putrefaction
with the resulting absorption of putrefactive products (indol,
skatol, and other toxins) is detrimental to the red blood cells and
may in this way interfere with the utilization and economy of
The beneficent therapeutic properties of citrus fruits have
been attributed to every constituent of citrus fruits, the oil in
the peel, citric acid, acid salts in the pulp, bitter principle present
in some, the vitamins and other constituents. Grapefruit has
been offered as a safeguard against malaria and influenza and
the oil has been considered as an elixir. It is well to examine
some of these constituents and determine if possible what value
they have and wherein it lies.
To Rumphius belongs the credit of discovering that the juices
of citrus fruits check perspiration and therefore quench thirst.
Such fruit juices stimulate the appetite, increase salivary secre-
tion, and cause diuresis. Not only do the juices of citrus fruits
have these effects but the juices of most of the fruits which con-
tain acids in appreciable amounts also produce the same results.
When fruit is eaten there is introduced into the digestive tract
a number of organic acids such as malic, citric, tartaric, acetic
and benzoic. The different fruit acids are composed of variable
amounts of carbon, hydrogen, and oxygen and their action in
the body is practically the same with the exception of benzoic
acid, which behaves in an entirely different way.
It is often very confusing to the housewife to read that the
eating of fresh fruits produces an alkaline reaction. If we con-
sider the citric acid and the potassium acid citrate of the orange
as an example the following explanation may prove helpful.
The acidity of the orange is largely due to potassium acid cit-
rate and to citric acid. When the juice of the orange is taken
into the digestive system its odor, pleasing taste, and acid prop-
erties increase the action of the salivary glands. The juice of
oranges has a pH of about 3.1. The citric acid and the potassium
acid citrate pass out of the stomach practically unchanged and
enter the duodenum, the first division of the small intestines.
Here the bases (sodium, potassium) of the bile and intestinal
juices react with the free citric acid and form a sodium or potas-

Florida Agricultural Experiment Station

sium salt. The acid salts already existing and the ones formed
with bile and intestinal juices are now absorbed into the blood.
Potassium acid citrate is the salt of a weak acid and a strong
base. It is oxidized in the blood and tissues to carbonic acid,
which decomposes into carbon dioxide and water and the free
bases, sodium and potassium. The carbon dioxide is thrown off
during respiration. The amount of base left is known as the
alkaline reserve.
Any excess of alkali above the reserve must be eliminated. The
chief mode of elimination is through the kidneys. When there
is a large excess of alkali to be eliminated the urine becomes less
acid and finally alkaline in reaction. Diuresis is caused by the
excretion of the alkaline salts according to the following mech-
anism: The presence of salts in the blood formed in the neutral-
ization of fruit acids increases the osmotic pressure and fluid
from the tissues is drawn into the blood. The capillary pressure
in the secreting portions of the kidneys (the glomeruli) is in-
creased, therefore, the excretion of water into the kidney
tubules is increased. The urine is secreted rapidly and there is
little danger of reabsorption of salts as is often the case when
the urine is secreted slowly. The excretion of urea, other salts,
and impurities is increased by the increase in the flow of urine.
For this reason the fruit acids are considered a decided advan-
tage in flushing the kidneys, especially in disease.
It was mentioned above that benzoic acid, found in cranberries
and prunes to a greater extent than in most of the other fruits,
behaves in a somewhat different way. It is changed into sodium
and potassium salts as are the other acids. After it is absorbed
by the kidneys it combines with one of the amino acids formed
by the digestion of protein, to form hippuric acid and is ex-
creted as such. This reaction takes place very quickly after the
ingestion of benzoic acid. The small amount of benzoic acid in
fruits or the small amount formed in the digestion of meat have
no known effect on human metabolism. When large amounts are
ingested free excretion of urine (diuresis) follows with the ex-
cretion of considerable amounts of hippuric acid and a reduction
of uric acid.
In considering how fruit acids are able to check perspiration
it is necessary to examine two different processes, first the physi-
ology of micturition (the secretion and elimination of urine);
second, the physiology of perspiration. According to physiolo-
gists of today urine is secreted through the glomeruli by a special

Bulletin 237, General Properties of Some Florida Fruits 29

secretary action of the endothelial cells. It appears that the
water and salts come mainly through the glomeruli, while the
urea comes from the cells of the convoluted tubules. The sweat
comes from special sweat glands scattered over the body. The
action of the sweat glands is dependent upon the nerve endings
which respond to the stimulation of heat. These impulses are
transmitted over sensory nerves to nerve centres controlling the
motor nerves of the sweat glands. The motor nerves stimulate
the activity of the sweat glands and an increased amount of
sweat is poured out upon the surface of the body. In general
it may be said that the functions of the kidneys as an excretory
organ and the skin as an excretory organ are inversely propor-
tional to each other. When the skin is secreting large amounts
of sweat the kidneys are secreting small amounts of urine. This
is the reason for the use of fruit acids in the summer:-The fruit
acids produce a diuresis, or increase the amount of urine, with-
out any other particular effect on the body; consequently the
amount of sweat is less and the person is more comfortable. It
is not to be inferred that a person should not perspire in the
summer but it does mean that more of the water excretion and
irritating substances can be thrown out by the way of the urine.
Fruit acids are used in various diseases to advantage. In ty-
phoid fever fruit acids are of value as an aid in the process of
washing out the system. They are frequently given in gout,
rheumatism, and chronic gastritis. In diseases where the elim-
ination of a considerable amount of water is beneficial, as in
Bright's disease, fruit acids are an advantage.
As previously mentioned, grapefruit contains the glucoside
naringen. This glucoside is very bitter even in dilute solutions.
The claim is often made that this naringen has the same physio-
logical action as quinine. So far as experimental evidence is
concerned, quinine and naringen have only one property in com-
mon, a bitter taste, and therefore belong to that class of drugs
known as bitters. It has been confirmed by modern scientific
investigation that the effect of bitters depends upon the taste,
and that it is useless to administer them in the form of pills.
Just how bitters act has not been fully demonstrated. When
they are given shortly before meals it is conceivable that they
may act as a chemical signal to set up reflexes which influence
appetite. According to Sollman (ref.), bitters may be used:
(1), To increase appetite, from whatever cause this may be de-
ficient. (2), To improve digestion in all kinds of atonic dys-

Florida Agricultural Experiment Station

pepsia, with motor or secretary deficiency. They tend to re-
move anorexia (loss of appetite), oppression, constipation, and
hypochondria (morbid condition). (3), As tonics in anaemia, in
convalescence, in wasting diseases, to hasten reconstruction.
(4), As anti-emetics (sedatives). It is possible that a part of the
therapeutic properties of grapefruit may be attributed to the
bitter principle, though thus far there is nothing to indicate
that naringen has been used as bitters.
The antiscorbutic (scurvy counteracting) action of fruits and
particularly of citrus fruits has been known for generations.
While most fruits are actively antiscorbutic in the fresh state,
citrus fruits seem to possess this property to a very great extent.
It appears to be definitely established that the most active prin-
ciple that is preventive and curative in citrus fruits is present
not in the peel but in the juice. This active principle has been
attributed to the acids, potassium and other salts, and has finally
been called vitamin C. While much data are available on the
subject of vitamin C the chemistry of this vitamin has made
little progress.
While it is shown in Table XI that there are other vitamins in
citrus and other fruits, the amounts are small and fruits are not
recommended as a rich source of these vitamins.

Fruit | A B C | D
Avocado ........................................ + ++ + +
Grapefruit juice (fresh) .......... + ++ +++
Grapefruit juice (dried) .......... ++ +++
Guava ....................................... + + +
Mango (dried) .................... ++
Mango (ripe and unripe)....... + ++
Papayas ...................................... ++ + +++
Pineapple (canned) .................. ++ ++ ++
Pineapple (raw) ........................ ++ ++ ++
Tangerine............................ +++
Orange juice (cone.) ................. ++ ++
Orange juice (dried) ....--......... ++ ++ +++
Orange juice (fresh) .................. ++ ++ +++
Orange juice (frozen stored) .. +
Orange peel (outer) .................. ++ + ++
+Indicates that the food contains the vitamin.
++Indicates that the food is a good source of the vitamin.
+++Indicates that the food is an excellent source of the vitamin.
*Indicates that evidence is lacking or appears insufficient.

It is a well known fact that the tannins so widely distributed
in vegetable principles, precipitate proteins and are, therefore,
astringent. Because tannins are contained in a number of bever-

Bulletin 237, General Properties of Some Florida Fruits 31

ages, as tea and certain wines and in certain fruits, particularly
in the persimmon, the effect of continued administration of small
amounts of tannin has considerable importance. The mild
astringent action may be locally tonic and beneficial, but large
quantities may prove irritant and may lead to gastro-enteritis.
Even small quantities of tannin interfere somewhat with absorp-
tion. However, these combinations are again decomposed in the
alkaline intestines, so that the interference is not large. On the
whole, it may be said that the small quantities of tannin con-
tained in vegetables and fruits are not injurious.
Robscheit-Robbins, Elden, Sperry and Whipple (14), working
on severe cases of anaemia, have found that the ash of apricots,
and to a lesser extent the ash of commercial pineapple, were sur-
prisingly potent in causing a large output of red coloring matter
of the blood (hemoglobin) above control levels. The elements
considered responsible for this increase in hemoglobin are iron
and copper. Other investigators are of the opinion that copper,
iron, nickel, cobalt, arsenic, iodine, bromine, and zinc play a role
in human metabolism. It is quite possible that when analyses
of fruits and vegetables include these and other elements the ash
of different fruits may show characteristic differences which
may explain some of the suggested therapeutic and nutritional
values of fruits. While fruits may contain constituents that
possess very valuable hygienic and medicinal properties, until
they are isolated and their physiological properties tested, we
may say that in the main the value of fruit in the diet depends
upon its bulk, upon the mineral salts, starches, glucosides,
sugars, and other substances present, upon its refreshing, appe-
tizing and laxative qualities, and upon its vitamin content.

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tent of avocados. Jour. Home Econ. 21:360-364. Illus. 1929.
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